Lubricating oil additives



United States Patent Ofiice 3,220,948 Fatented Nov. 30, 1965 3,220,948 I LUBRICATING OIL ADDITIVES Johannes Reese, Wiesbaden, and Berthold Briihler, Fulda,

Germany, assignors to Chemische Werke Albert, Wiesbaden-Biebrich, Germany, a corporation of Germany No Drawing. Filed Mar. 20, 1962, Ser. No. 131,172 Claims priority, application Germany, Mar. 24, 1961, C 23,726 16 Claims. (Cl. 25246.6)

The invention relates to novel lubricating additives for improving the properties of lubricating oils. The invention also relates to improved lubricating oils containing the novel lubricating additives.

It is well known that lubricating oils such as refined mineral oils do not meet the standards required for their use as engine oils or transmission lubricants. Attempts to overcome the disadvantages of oils such as those prepared by petroleum distillation or by the Fischer-Tropsch synthesis have led to the use of different types of additives. The resulting oils are called alloyed oils.

One of the principal defects of the basic oils is their inadequate temperature-viscosity index. Another defect is their loss of uniform films on metal surfaces when under pressure. For example, at points of transmission of heavy weights such as when gear wheels pass over a transmission gear the oil films frequently break so that the conditions and wear values are almost that of dry operation.

The transmission and engine oils also require anticorrosive properties to prevent the corrosion of the lubricated parts and the oil itself. The corrosion by oil and the aging of the oil, i.e., the degradation of the oil is catalytically favored particularly in the presence of oxygen, by metallic particles, formed by abrasion. Therefore, in order to be satisfactory, the additives must act as inhibitors.

Two very important effects which are obtained by the addition of additives to the oil are the detergent effect and the dispersent effect. These additives are usually referred to as HD or DD additives which are abbreviations for heavy duty or detergent-dispersent additives. These additives clean the lubricated parts by automatically removing metallic residues and carbonization residues from the lubricated surfaces and dispersing the said residues in the oil.

All of the afore-said problems involve surface tension problems and therefore it is not surprising that most oil additives have surface active properties, are similar in principle, and their ranges of activity frequently overlap. The additives have a strongly polar portion and an oleophilic portion in their molecules. The surface active additives form a sort of adhesive bridge between the metal and the oil since the oleophilic portion of the molecule projects into the oil while the polar portion of the molecule covers the metal surface. This gives a better mechanic capacitance to the oil film.

Many compounds ranging from simple metal soaps to complex sulfur-phosphorus compounds have been proposed as lubricating oil additives. Many patents describe the reflux reaction products of partly oxygen-free, partly oxygen-containing low molecular weight or high molecu lar weight organic compounds with phosphorus-sulfides which may subsequently be treated with metal oxides, such as the oxides of barium, calcium or zinc. Special attention has been given to dithiophosphoric acid esters and their salts which are prepared by the reaction of high molecular weight alcohols with phosphorus-pentasulfide followed by neutralization of the acid esters with a metal oxide to form salts such as Zn-0,0-dihexyldithiophosphate. It has also been proposed to use mixtures of derivatives of dithiophosphoric acid and organic polysulfides. In German Auslegeschrift No. 1,042,807 there are described lubricating oil additives consisting of mixtures of a phosphoric compound selected from the group consisting of (A) an oil soluble dithiophosphoric acid triester, a metal salt of dithiophosphoric acid diesters, a bis-(dithiophosphoric acid diester) or a dithiophosphoric acid diester-thioanhydride and (B) an oil soluble turpentine-polysulfide or an oil soluble di-,aralkyl) polysulfide. However, satisfying results are obtained only by using critical amounts of the two components. Recently efforts have been made to obtain ash-free additives which have not been available.

It is an object of the invention to provide novel lubricating additives for improving the dispersent-detergent properties of lubricating oils.

It is another object of the invention to provide improved lubricating oils containing novel lubricating additives.

These and other objects and advantages of the invention will become obvious from the following detailed description.

The lubricating additives of the invention are compatible in all proportions with the lubricating oils and consist of a combination product, i.e., a mixture or a reaction product, of (A) 10 to by weight of one or more 0,0-diesters of dithiophosphoric acid and a monohydric aliphatic alcohol which esters are already known as lubricating additives, and (B) 90 to 10% by weight of the reaction product of sulfur and a diester of an a,B-unsaturated dicarboxylic acid and a monohydric aliphatic alcohol. As the term aliphatic indicates, the characteristic feature of these radicals is their non-aromatic structure, and therefore the term aliphatic is generic for cycloaliphatic, too. The monohydric aliphatic alcohols consist of an OH-group and hydrocarbon radicals having 4 to 22 carbon atoms. The reaction product of sulfur and said diester is hereinafter referred to as sulfurized ester. Preferably the mixtures contain 30 to 70% by weight of the said dithiophosphoric acid ester and 70 to 30% by weight of the said reaction product Examples of suitable cad-unsaturated dicarboxylic acids whose esters may be used are itaconic acid, mesaconic acid, citraconic acid, maleic acid and fumaric acid. Maleic acid and fumaric acid are the preferred acids.

The alcohols from which the alkyl portion of the esters are derived are branched or straight chain aliphatic or cycloaliphatic hydrocarbon alcohols which have 4 to 22 carbon atoms. Examples of suitable alcohols are butyl alcohol, isobutyl alcohol, cyclohexanol, 2-ethylhexanol, n-octanol, diisobutanol, dodecyl alcohol alcohol, oleyl alcohol, stearyl alcohol, commercial mixtures of fatty alcohols, i.e. those obtained by a hydrolysis of fats or fatty oils of natural origin such as coconut oil or lard or of ester waxes and subsequent hydrogenation, e.g., alcohols having 12 to 18 carbon atoms, etc.

The components can be mixed at temperatures ranging from room temperature to 200 C., preferably between room temperature and C. If the components are mixed at temperatures higher than room temperature, a reaction takes place. If the mixing is carried out at a relatively low temperature such as room temperature, the mixture may be subsequently heated to a higher temperature to cause a reaction.

The lubricating oils to which the additives of the invention are added are animal, vegetable, mineral or synthetic oils. It is preferred, however, to use oils obtained in the petroleum industry. The improved lubricating oils contain 0.2 to 10%, preferably 0.5 to 3%, by weight of the additive mixture calculated on the basis of the weight of the lubricating oil. The lubricating oil products have properties satisfactory for HD and EP oils and may be used for various purposes such as breaking-in oils for engines or hypoid gear oil-s. Other known lubricating additives may be added to the improved lubricating oils such as additives for improving the temperature-viscosity index.

The 0,0-dialkyldithiophosphoric acid esters are known compounds and can be prepared by known means. For example, the alcohol to be reacted is dissolved in an inert organic solvent and while maintaining the mixture at a slightly elevated temperature, the phosphorus pentasulfide 4 beolen, Erddl and Kohle, vol. 7 (1954), p. 64042, was carried out.

IFE test A basic oil of the Deutsche Gasolin-Nitag type (Type SAE 90, d =0.918) was used for the tests. The additives to be tested were added to the basic oil so that the basic oil contained 2% by weight of the additives. The results of the tests are summarized in Table I.

TABLE I Initial and end tem- Wear value perature, C. Additive Type of testing in grams X10- Sliding trace On the surface With oil Without oil Feeding Feeding None Normal 33. 94/116 Many thin grooves, dark gray.

0.80 92/118 Smooth, slightly violet. High speed 4. 82 176/204 Smooth, violet with light yellow foundation (tarnishing color of the steel), dark 0,0-dialkyldithiophosphoric blue tarnishing color besides the sliding acid ester. traces.

Emergency test without oil 2.20 97/120 120/166 Isolated thin grooves, foundation of the (after 19 minutes and grooves a dark gray. seconds). Sulphurized fumaric acid Normal 3.01 92/113 Finest grooves, dark brown with a violet dibutyl ester. sheen.

Normal 0.98 81/81 Apart from some isolated finest grooves, High speed 0. 58 73/71 smooth, violet, good cooling activity, Additive of Example I separation on the sliding trace.

Emergency test without oil 2. 88 89/113 86/147 Smooth, violet.

(after 43 minutes).

Normal-test: 3 hours at 150 r.p.m.,* sliding speed 0.2 m/second, bearing pressure 4,500 kgJcmfl. High speed: 1 hour at 450 r.p.m.,* sliding speed 0.6 m/second, bearing pressure 4,500 kgJcmJ.

Emergency test without oil: 3 hours normal test, then oil feeding was st stopped (indication of the time and of the wear value at this moment).

*R.p.m.=revolutions per minute.

is gradually added until the reaction is completed. After filtration and elimination of the solvent, the product can be purified by distillation or crystallization of its salts although purification is not required.

The sulfurized ester of the c p-unsaturated carboxylic acids may be prepared by a process similar to that described by Michael, Berichte der Deutschen Chem. Gesellschaft, vol. 28 (1895), p. 1633, or by Flet-t et al., Malei-c Anhydride Derivatives (1952), p. 219. Thus, for example, one mol of diethyl fumarate is heated with one gramatom or an excess of sulfur at an elevated temperature until completion of the reaction; the mixture is then cooled and the unreacted ester and sulfur are separated from the product. Michael refers to his reaction product as episulfidosuccinic acid diethylester but we believe the product to be a dimer, possibly 1,4-dithia-cyclohexane- 2,3,4,5-tetracarboxylic acid tetraethylester, because of its molecular weight determination and its behavior during the reaction.

In the following examples there are described several preferred embodiments to illustrate the invention. However, it should be understood that the invention is not intended to be limited to the specific embodiment.

EXAMPLE I 251 arts by weight of an 0,0-dialkyl-dithiophosphoric acid ester wherein the alkyl radicals are derived from a commercial mixture of fatty alcohols having 12 to 18 carbon atoms and which has an acid number of 100 were heated with 130 parts by weight of a sulfurized dibutyl fumarate reaction product for 12 hours at 120 C., 370 parts of a dark brown, clear oil of n =1.4780 were obtained. The product was compatible in all proportions with lubricating oils.

To illustrate the superior efficiency of the additives of the invention the IFE test described by Bartel et al., Untersuchungen iiber Verschleiss und Reibung, Schmiertechnik, vol 3, issue 4 (1956), p 184491 and FZG- gear wheel-short test of Niemann et al., Erfahrungen mit der Getriebeolpriifung im Zahnradverspannungspriifstand, Erd'cil and Kohle, vol. 12 (1959), p. 472-80, and Der FZG'Zflhl'lYfld'KllI'ZIESI zur lriifung von Getrieopped, at the moment that the piston started to seize the apparatus was FZG-gear wheel-short test This test was conducted with the same basic oil as the IFE test containing 2% by weight of the additive of Example I. Also tested were the basic oil and a standard alloyed oilnow sold commercially. The rotary speed (v) was 8.3 m./ second at 2,175 r.p.m. with the initial temperature of the oil container at C. The sliding speed on the tooth crest (V was 0.675 -v m./second. The basic oil failed at a load range of 7 and the commercial alloyed oil failed at a load range of 10. In contrast thereto, the basic oil containing the additive of Example I had a load range of above 12, the maximum obtainable. This means EXAMPLE n 121 parts by weight of dithiophosphoric acid-0,0-di- (isobutyl) ester were mixed with 130 parts by weight of a sulfurized product of di-(isobutyl) fumarate and the mixture was heated for 6 hours at C. A dark brown oil of n :1.4860 was obtained which could be mixed with lubricating oils in any desired proportion. The IFE test of this product showed that it was a suitable additive for preparing breaking-in engine oils.

EXAMPLE III 151 parts by weight of a dithiophosphoric acid-0,0-dialkylester were mixed with 60 parts by weight of a sulfurized dialkyl fumarate at room temperature and a medium brown, clear oily product was obtained which was compatible with lubricating oils in any proportion. The alkyl radicals of the said esters were derived from a mixture of fatty alcohols having 12 to 18 carbon atoms. When the product was added to a basic oil in an amount of 5% by weight, a gear oil of good quality was obtained.

EXAMPLE IV 151 parts by weight of a dithiophosphoric acid-0,0-di alkylester wherein the alkyl radicals were derived from fatty alcohols having 12 to 18 carbon atoms was mixed with 112 parts by weight of a sulfurized di-(Z-ethylhexyl) fumarate for 25 hours at 120 C. A brown oil of was obtained. The said oil was compatible in any desired proportion with lubricating oils and was a suitable additive for gear oils.

EXAMPLE V 30 parts by weight of dithiophosphoric acid-0,0-dibutylester was mixed at room temperature with 130 parts by weight of a sulfurized dibutyl fumarate. The resulting composition was a suitable additive for the preparation of breaking-in engine oils.

Various modifications of the products of the invention may be made without departing from the spirit or scope thereof, and it is to be understood that the invention is to be limited only as defined in the appended claims.

We claim:

1. A lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) to 90% by weight of a dithiophosphoric acid-0,0- dialiphatic ester and (B) 90 to 10% by weight of the reaction product of sulfur and a dialiphatic ester of an t p-ethylenically unsaturated dicarboxylic acid wherein the aliphatic radicals are hydrocarbon radicals having 4 to 22 carbon atoms.

2. The additive of claim 1 wherein the a e-unsaturated dicarboxylic acid is selected from the group consisting of maletic acid and fumaric acid.

3. A lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0- dialiphatic ester and (B) 70 to 30% by weight of the reaction product of sulfur and a dialiphatic ester of an 6- ethylenically unsaturated dicarboxylic acid wherein the aliphatic radicals are hydrocarbon radicals having 4 to 22 carbon atoms.

4. A lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0- dialkylester wherein the alkyl radicals are derived from a mixture of fatty alcohols having 12 to 18 carbon atoms and (B) 70 to 30% by weight of a sulfurized product of dibutyl fumarate.

5. A lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of 30 to 70% by weight of a dithiophosphoric acid-0,0-di- (isobutyl)-ester and (B) 70 to 30% by weight of a sulfurized product of di-(isobutyl) fumarate.

6. A lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0-dialkylester and (B) 70 to 30% by weight of a sulfurized product of dialkyl fumarate wherein the alkyl radical of the esters are derived from a mixture of fatty alcohols having 12 to 18 carbon atoms.

7. A lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0- dialkylester wherein the alkyl radicals are derived from a mixture of fatty alcohols having 12 to 18 carbon atoms and (B) 70 to 30% by weight of a sulfurized product of di-(2-ethylhexyl) fumarate.

8. A lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of dithiophosphoric acid-0,0-di- 6 butylester and (B) 70 to 30% by weight of a sulfurized product of dibutyl fumarate.

0. An improved lubricating oil comprising a major amount of an oil suitable as a base in lubricating oils and containing 0.2 to 10% calculated on the weight of the oil, of a lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 10 to by weight of a dithiophosphoric acid-0,0-dialiphatic ester and (B) 90 to 10% by weight of the reaction product of sulfur and a dialiphatic ester of an x,,8- ethylenically unsaturated dicarboxylic acid wherein the aliphatic radicals are hydrocarbon radicals having 4 to 22 carbon atoms.

10. The lubricating oil of claim 9 wherein the amount of lubricating oil additive is 0.5 to 3% by weight.

11. The lubricating oil of claim 9 wherein the a,,8- ethylenically unsaturated dicarboxylic acid is selected from the group consisting of maleic acid and fumaric acid.

12. An improved lubricating oil comprising a major amount of an oil suitable as a base in lubricating oils and containing 0.2 to 10%, calculated on the weight of the oil, of a lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0- dialkylester wherein the alkyl radicals are derived from a mixture of fatty alcohols having 12 to 18 carbon atoms and (B) 70 to 30% by weight of a sulfurized product of dibutyl fumarate.

13. An improved lubricating oil comprising a major amount of an oil suitable as a base in lubricating oils and containing 0.2 to 10%, calculated on the weight of the oil, of a lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0- di-(isobutyl)-ester and (B) 70 to 30% by weight of a sulfurized product of di-(isobutyl) fumarate.

14. An improved lubricating oil comprising a major amount of an oil suitable as a base in lubricating oils and containing 0.2 to 10%, calculated on the weight of the oil, of a lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0- dialkylester and (B) 70 to 30% by weight of a sulfurized product of dialkyl fumarate wherein the alkyl radicals of the esters are derived from a mixture of fatty alcohols having 12 to 18 carbon atoms.

15. An improved lubricating oil comprising a major amount of an oil suitable as a basein lubricating oils and containing 0.2 to 10%, calculated on the weight of the oil, of a lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of a dithiophosphoric acid-0,0- dialkylester wherein the alkyl radicals are derived from a mixture of fatty alcohols having 12 to 18 carbon atoms and (B) 70 to 30% by weight of a sulfurized product of di-(Z-ethylhexyl) fumarate.

16. An improved lubricating oil comprising a major amount of an oil suitable as a base in lubricating oils and containing 0.2 to 10%, calculated on the weight of the oil, of a lubricating oil additive consisting of a reaction product formed by heating up to 200 C. a mixture of (A) 30 to 70% by weight of dithiophosphoric acid-0,0- dibutylester and (B) 70 to 30% by weight of a sulfurized product of dibutyl fumarate.

References Cited by the Examiner UNITED STATES PATENTS 2,220,843 11/1940 Johnson 25248.6 X 2,242,260 5/ 1941 Prutton 29246.6 2,773,861 12/1956 Musselman 25246.6 X 2,827,434 3/ 1958 Wierber 25248.6 X

DANIEL E. WYMAN, Primary Examiner. ALPHONSO D. SULLIVAN, Examiner. 

9. AN IMPROVED LUBRICATING OIL COMPRISING A MAJOR AMOUNT OF AN OIL SUITABLE AS A BASE IN LUBRICATING OILS AND CONTAINING 0.2 TO 10% CALCULATED ON THE WEIGHT OF THE OIL, OF A LUBRICATING OIL ADDITIVE CONSISTING OF A REACTION PRODUCT FORMED BY HEATING UP TO 200*C. A MIXTURE OF (A) 10 TO 90% BY WEIGHT OF A DITHIOPHOSPHORIC ACID-O,O-DIALIPHATIC ESTER AND (B) 90 TO 10% BY WEIGHT OF THE REACTION PRODUCT OF SULFUR AND A DIALIPHATIC ESTER OF AN A,BETHYLENICALLY UNSATURATED DICARBOXYLIC ACID WHEREIN THE ALIPHATIC RADICALS ARE HYDROCARBON RADICALS HAVING 4 TO 22 CARBON ATOMS. 